Silicon oxide film formation method, silicon oxide film formation apparatus, and silicon oxide film

Abstract

This silicon oxide film formation method comprises: a step for introducing, from a gas introduction unit (35), a processing gas for forming a silicon oxide film (210) on a substrate (200) to be processed in a processing chamber (10); a step for applying AC power having a first frequency to the gas introduction unit; and a step for applying AC power having a second frequency higher than the first frequency to the gas introduction unit. The step for applying AC power of the first frequency and the step for applying AC power of the second frequency are alternately switched and performed.

Description

Method for forming a silicon oxide film, apparatus for forming a silicon oxide film, and silicon oxide film

[0001] This invention relates to a method for forming a silicon oxide film, an apparatus for forming a silicon oxide film, and a silicon oxide film.

[0002] Conventionally, a method for forming a silicon oxide film on a substrate is known. Such a silicon oxide film formation method is disclosed, for example, in Japanese Patent Publication No. 6183965.

[0003] Japanese Patent Publication No. 6183965 discloses a method for forming a silicon oxide film on a substrate by a parallel-plate type plasma CVD method, in which a processing gas for forming a silicon oxide film on a substrate to be processed is introduced from a gas inlet into a processing chamber, a relatively high frequency AC power is applied to the gas inlet, and a relatively low frequency AC power is applied to a stage on which the substrate is placed. Furthermore, in the silicon oxide film formation method of Japanese Patent Publication No. 6183965, in order to suppress the change in the stress value of the silicon oxide film over time, after the silicon oxide film is formed on the substrate, a modified layer is formed on the surface of the silicon oxide film by plasma treatment with a rare gas.

[0004] Patent No. 6183965

[0005] In the aforementioned Japanese Patent Publication No. 6183965, in order to suppress the change in stress value of a silicon oxide film over time, a modified layer is formed on the surface of the silicon oxide film by plasma treatment with a rare gas after the silicon oxide film has been formed on a substrate. Therefore, after the silicon oxide film has been formed, it is necessary to introduce a rare gas and perform plasma treatment in order to form the modified layer. In this case, in order to form a modified layer on the silicon oxide film, it is necessary to change the treatment gas after the silicon oxide film has been formed. As a result, it is difficult to improve the production efficiency (throughput) of silicon oxide films in which the change in stress value over time is suppressed. Therefore, it is desirable to improve the production efficiency of silicon oxide films in which the change in stress value over time is suppressed.

[0006] This invention was made to solve the above-mentioned problems, and one of its objectives is to provide a silicon oxide film formation method and a silicon oxide film formation apparatus that can improve the production efficiency of silicon oxide films in which changes in stress values ​​over time are suppressed.

[0007] To achieve the above objective, the inventors of this application conducted intensive studies and found that by providing a process for forming a silicon oxide film on a substrate to be processed in a processing chamber through a gas inlet, applying AC power of a first frequency to the gas inlet, and applying AC power of a second frequency higher than the first frequency to the gas inlet, and by alternately switching between the steps of applying AC power of the first frequency and AC power of the second frequency, it is possible to obtain a silicon oxide film in which the change in stress value over time is suppressed, even without forming a modified layer.

[0008] In other words, the silicon oxide film formation method according to the first aspect of this invention comprises the steps of: introducing a processing gas for forming a silicon oxide film on a substrate to be processed in a processing chamber from a gas inlet; applying AC power of a first frequency to the gas inlet; and applying AC power of a second frequency higher than the first frequency to the gas inlet, wherein the steps of applying AC power of the first frequency and applying AC power of the second frequency are performed by switching between them alternately.

[0009] In the silicon oxide film formation method according to the first aspect of this invention, as described above, the process is performed by alternately switching between the step of applying AC power of a first frequency to the gas introduction section and the step of applying AC power of a second frequency, which has a higher frequency than the first frequency, to the gas introduction section. This makes it possible to form a silicon oxide film in which the change in stress value over time is suppressed. This point has been confirmed by experiments (examples) described later. As a result, since there is no need to provide a step of forming a modified layer, the production efficiency (throughput) of silicon oxide films in which the change in stress value over time is suppressed can be improved. In addition, since it is not necessary to apply AC power of a relatively low frequency to the stage on which the substrate is placed, it is possible to suppress the high-energy collision of the plasma-generated processing gas with the substrate. As a result, it is possible to suppress defects in the substrate caused by plasma collisions. This makes it possible to form a silicon oxide film in which the change in stress value over time is suppressed without applying AC power to the substrate side. Here, in Japanese Patent Publication No. 6183965, AC power is applied to the substrate side to draw in ions in the plasma. However, given the current state of device technology, plasma damage can negatively impact devices, making it increasingly difficult to apply AC power to draw ions from the plasma to the substrate, as described above. Therefore, there is a need to eliminate the change in stress values ​​over time without applying AC power to the substrate (i.e., without causing plasma damage).

[0010] In the silicon oxide film formation method according to the first aspect described above, preferably, the steps of applying AC power of a first frequency and applying AC power of a second frequency are alternately performed multiple times each. With this configuration, the total number of silicon oxide film layers formed by the steps of applying AC power of the first frequency and the steps of applying AC power of the second frequency can be made to four or more, thereby stabilizing the film quality of the silicon oxide film.

[0011] In the silicon oxide film formation method according to the first aspect described above, preferably, the process involves applying AC power of a first frequency and applying AC power of a second frequency, with the first frequency AC power being applied first, and then the process of applying AC power of a first frequency and the second frequency AC power being alternately switched between. With this configuration, a silicon oxide film layer is formed by applying AC power of a relatively low frequency, the first frequency, first, so a layer with compressive stress can be formed on the substrate first. This makes it easier for the silicon oxide film to adhere to the substrate.

[0012] In the silicon oxide film formation method according to the first aspect described above, preferably, in the step of introducing the processing gas from the gas introduction section, tetraethoxysilane (TEOS) gas is introduced. With this configuration, the tetraethoxysilane (TEOS) gas is plasma-generated, and a silicon oxide film with suppressed changes in stress values ​​over time can be easily formed on the substrate.

[0013] In the silicon oxide film formation method according to the first aspect described above, preferably, the stress value of the formed silicon oxide film is adjusted by adjusting the ratio of the application time between the step of applying AC power of a first frequency and the step of applying AC power of a second frequency. With this configuration, a silicon oxide film having a desired stress value and in which the change in stress value over time is suppressed can be formed on the substrate.

[0014] To achieve the above objective, the silicon oxide film forming apparatus according to the second aspect of the present invention comprises a processing chamber on which a substrate to be processed is placed, a gas introduction unit for introducing a processing gas for forming a silicon oxide film on the substrate in the processing chamber, an AC power application unit for applying AC power to the gas introduction unit, and a control unit. The control unit controls the introduction of the processing gas from the gas introduction unit and alternately switches the AC power applied from the AC power application unit between AC power of a first frequency and AC power of a second frequency having a higher frequency than the first frequency.

[0015] In the silicon oxide film forming apparatus according to the second aspect of the present invention, as described above, the control unit controls the alternating current power applied from the AC power application unit to the gas introduction unit to alternately switch between AC power of a first frequency and AC power of a second frequency which has a higher frequency than the first frequency. This makes it possible to form a silicon oxide film in which the change in stress value over time is suppressed. This point has been confirmed by experiments (examples) described later. As a result, since there is no need to provide a step for forming a modified layer, it is possible to provide a silicon oxide film forming apparatus that can improve the production efficiency (throughput) of silicon oxide films in which the change in stress value over time is suppressed. Furthermore, since relatively low frequency AC power is not applied to the stage on which the substrate is placed, it is possible to suppress the high-energy collision of the plasma-generated processing gas with the substrate. As a result, it is possible to suppress defects in the substrate caused by plasma collisions.

[0016] A silicon oxide film according to the third aspect of the present invention comprises a first layer having compressive stress and a second layer having tensile stress, wherein the first and second layers are stacked alternately in multiple layers, and in the state where the first and second layers are stacked in multiple layers, the film has a tensile stress of +100 MPa or more, and the change in film stress after one day has elapsed since formation is 20 MPa or less.

[0017] In the silicon oxide film according to the third aspect of the present invention, by configuring it as described above, it is possible to provide a silicon oxide film in which the change in stress value over time is suppressed. This has been confirmed by experiments (examples) described later. As a result, since there is no need to provide a step for forming a modified layer, it is possible to provide a silicon oxide film that can improve the production efficiency (throughput) of a silicon oxide film in which the change in stress value over time is suppressed.

[0018] According to the present invention, as described above, it is possible to improve the production efficiency of silicon oxide films in which the change in stress values ​​over time is suppressed.

[0019] This is a schematic diagram showing the general configuration of a substrate processing apparatus. This is a flow chart for explaining a silicon oxide film formation method. This is a schematic diagram showing a silicon oxide film formed by the silicon oxide film formation method. This is a graph showing the film stress as a function of the time ratio between low frequency and high frequency when the AC power applied to the upper part is alternately switched between low frequency and high frequency according to the example. This is a graph showing the etching rate as a function of the time ratio between low frequency and high frequency when the AC power applied to the upper part is alternately switched between low frequency and high frequency according to the example. This is a graph showing the film stress as a function of high frequency power when the AC power applied to the upper part is set to a high frequency according to Comparative Example 1. This is a graph showing the etching rate as a function of high frequency power when the AC power applied to the upper part is set to a high frequency according to Comparative Example 1. This is a graph showing the film stress as a function of low frequency power when the AC power applied to the upper part is set to a low frequency according to Comparative Example 2. This is a graph showing the etching rate as a function of low frequency power when the AC power applied to the upper part is set to a low frequency according to Comparative Example 2. This graph shows the film stress against the power of the low-frequency power at the bottom when the AC power applied to the top is at a high frequency and the AC power applied to the bottom is at a low frequency, according to Comparative Example 3. This graph shows the etching rate against the power of the low-frequency power at the bottom when the AC power applied to the top is at a high frequency and the AC power applied to the bottom is at a low frequency, according to Comparative Example 3. This graph shows the film stress against the power of the high-frequency power at the top when the AC power applied to the top is at a high frequency and the AC power applied to the bottom is at a low frequency, according to Comparative Example 4. This graph shows the etching rate against the power of the high-frequency power at the top when the AC power applied to the top is at a high frequency and the AC power applied to the bottom is at a low frequency, according to Comparative Example 4. This graph shows the film stress against the etching rate immediately after film formation according to the Examples and Comparative Examples. This graph shows the film stress against the etching rate after time has passed, according to the Examples and Comparative Examples.

[0020] Embodiments of the present invention will be described below with reference to the drawings.

[0021] Referring to Figure 1, a substrate processing apparatus 100 that performs the substrate processing method of this embodiment will be described.

[0022] (Substrate Processing Apparatus) As shown in Figure 1, the substrate processing apparatus 100 is a parallel-plate type plasma processing apparatus that generates plasma in a processing chamber 10 to form a film on a substrate 200. In other words, the substrate processing apparatus 100 is a parallel-plate type plasma CVD apparatus. The substrate 200 is a semiconductor wafer formed from materials such as silicon, quartz glass, borosilicate glass, silicon carbide, gallium arsenide, or sapphire. Note that the substrate processing apparatus 100 is an example of a "silicon oxide film forming apparatus" within the scope of the claims.

[0023] The substrate processing apparatus 100 comprises a processing chamber 10, a substrate mounting section 20, a gas supply device 30, an AC power supply device 40, an exhaust device 50, a heater 60, and a control unit 70.

[0024] The processing chamber 10 has a closed space covered by the housing 11, and the substrate mounting section 20 is housed within the closed space of the housing 11. The substrate 200 to be processed is placed in the processing chamber 10.

[0025] The substrate mounting section 20 includes a stage 21 on which the substrate 200 is placed. The stage 21 is provided to be able to move up and down within the processing chamber 10 by a lifting cylinder 22.

[0026] The gas supply device 30 supplies a processing gas to the processing chamber 10 for processing the substrate 200. The gas supply device 30 supplies a processing gas to form a silicon oxide film 210 (see Figure 3) inside the processing chamber 10. Specifically, the gas supply device 30 supplies oxygen (O ２ ) Supplying gas O ２The system includes a gas supply unit 31, a TEOS gas supply unit 32 for supplying tetraethoxysilane (TEOS) gas, and a rare gas supply unit 33 for supplying rare gases (helium or argon). The processing gases supplied from each gas supply unit are introduced into the processing chamber 10 via branched supply pipes 34 for gas supply, through a gas introduction unit 35 provided in the processing chamber 10. In other words, the gas introduction unit 35 introduces processing gas to form a silicon oxide film 210 on the substrate 200 inside the processing chamber 10. The gas introduction unit 35 is a showerhead gas introduction unit.

[0027] The AC power supply device 40 supplies AC power to the processing chamber 10. The AC power supply device 40 includes a low-frequency power application unit 41 and a high-frequency power application unit 42 that supply AC power to the upper electrode (gas introduction unit 35) in order to plasmaize the processing gas in the processing chamber 10. The AC power supply device 40 also includes a lower AC power application unit 43 that supplies AC power to the lower electrode (stage 21) in order to supply AC power for the bias potential. The AC power supply device 40 also includes a switching unit 44 that switches the AC power supplied to the upper electrode (gas introduction unit 35) between the low-frequency power application unit 41 and the high-frequency power application unit 42. Note that the low-frequency power application unit 41 and the high-frequency power application unit 42 are examples of the "AC power application unit" as defined in the claims.

[0028] The low-frequency power application unit 41 and the high-frequency power application unit 42, which supply AC power to the upper electrodes, apply AC power to the gas introduction unit 35. The low-frequency power application unit 41 supplies AC power at a relatively low frequency. For example, the low-frequency power application unit 41 supplies AC power with a frequency of several Hz to several hundred kHz. The low-frequency power application unit 41 also supplies AC power with a power of 10W to 500W. The high-frequency power application unit 42 supplies AC power at a relatively high frequency. For example, the high-frequency power application unit 42 supplies AC power with a frequency of several MHz to several tens of MHz. The high-frequency power application unit 42 also supplies AC power with a power of 10W to 500W.

[0029] The lower AC power application unit 43, which supplies AC power to the lower electrodes, applies AC power to the stage 21 on which the substrate 200 is placed. The lower AC power application unit 43 supplies AC power at a relatively low frequency. For example, the lower AC power application unit 43 supplies AC power with a frequency of several kHz to several hundred kHz. The lower AC power application unit 43 also supplies AC power with a power of 10W to 500W.

[0030] The switching unit 44, under the control of the control unit 70, switches the power supply device electrically connected to the gas introduction unit 35 between the low-frequency power application unit 41 and the high-frequency power application unit 42.

[0031] The exhaust device 50 reduces the pressure inside the processing chamber 10. The exhaust device 50 includes a vacuum pump 51 that exhausts the gas inside the processing chamber 10 and an exhaust pipe 52 that connects the vacuum pump 51 to the processing chamber 10. Through the exhaust pipe 52, the vacuum pump 51 exhausts the gas inside the processing chamber 10, bringing the processing chamber 10 to a predetermined pressure state that is close to a vacuum.

[0032] The heater 60 heats the processing chamber 10. Specifically, the heater 60 includes a heater 61 that heats the substrate 200 and a heater 62 that heats the gas introduction section 35. Heater 61 heats the stage 21 to approximately 200°C, for example. Heater 62 heats the gas introduction section 35 to approximately 200°C, for example.

[0033] The control unit 70 controls each part of the substrate processing apparatus 100. Specifically, it controls the gas supply device 30 and the AC power supply device 40 to control the process of forming the silicon oxide film 210 on the substrate 200.

[0034] (Method for forming a silicon oxide film) Next, an overview of the silicon oxide film formation method of this embodiment will be described.

[0035] The silicon oxide film formation method of this embodiment includes the steps of: introducing a processing gas for forming a silicon oxide film 210 onto a substrate 200 to be processed in a processing chamber 10 from a gas introduction section 35; applying AC power of a first frequency (low frequency) to the gas introduction section 35; and applying AC power of a second frequency (high frequency) which is higher than the first frequency to the gas introduction section 35. In the silicon oxide film formation method of this embodiment, the steps of applying AC power of the first frequency (low frequency) and applying AC power of the second frequency (high frequency) are performed by switching between them alternately.

[0036] The silicon oxide film formation method of this embodiment is carried out by processing with the substrate processing apparatus 100. Specifically, in order to perform the silicon oxide film formation method, the control unit 70 of the substrate processing apparatus 100 controls the introduction of processing gas from the gas introduction unit 35 and the alternating current power applied from the low-frequency power application unit 41 and the high-frequency power application unit 42 to alternately switch between alternating current power of a first frequency (low frequency) and alternating current power of a second frequency (high frequency) which has a higher frequency than the first frequency.

[0037] In the step of applying AC power of a first frequency to the gas introduction section 35, AC power with a frequency of several kHz to several hundred kHz is supplied from the low-frequency power application section 41, and AC power of a first frequency (low frequency) is applied to the gas introduction section 35. In the step of applying AC power of a second frequency to the gas introduction section 35, AC power with a frequency of several MHz to several tens of MHz is supplied from the high-frequency power application section 42, and AC power of a second frequency (high frequency) is applied to the gas introduction section 35.

[0038] Furthermore, in the process of alternately switching between the process of applying AC power of a first frequency (low frequency) and the process of applying AC power of a second frequency (high frequency), the control unit 70 controls the switching unit 44 to alternately switch the power supply device electrically connected to the gas introduction unit 35 between the low-frequency power application unit 41 and the high-frequency power application unit 42.

[0039] Furthermore, in the silicon oxide film forming method of the present embodiment, the step of applying AC power of a first frequency (lower frequency) and the step of applying AC power of a second frequency (higher frequency) are alternately switched such that each of the steps is performed a plurality of times (two or more times). Preferably, the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately switched such that each of the steps is performed 10 times or more. More preferably, the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately switched such that each of the steps is performed 15 times or more. Further, preferably, the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately switched such that each of the steps is performed 30 times or less. More preferably, the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately switched such that each of the steps is performed 20 times or less.

[0040] Furthermore, in the silicon oxide film forming method of the present embodiment, the step of applying AC power of a first frequency (lower frequency) and the step of applying AC power of a second frequency (higher frequency) are alternately switched at intervals of 1 second or more and 100 seconds or less. Preferably, the switching is performed alternately at intervals of 2 seconds or more and 100 seconds or less. By setting the switching interval to 2 seconds or more, it is possible to suppress the influence of fluctuations such as unstable plasma or plasma fluctuation during plasma ignition (for example, reflected waves are generated when the set effective power is not applied).

[0041] Furthermore, in the silicon oxide film forming method of the present embodiment, the stress value of the formed silicon oxide film 210 is adjusted by adjusting the ratio of the application time between the step of applying AC power at a first frequency and the step of applying AC power at a second frequency. That is, the stress value of the silicon oxide film 210 is adjusted by adjusting the time for applying AC power at the first frequency (low frequency) and the time for applying AC power at the second frequency (high frequency). Specifically, by increasing the ratio of the time for applying AC power at the first frequency (low frequency) to the total application time (reducing the ratio of the time for applying AC power at the second frequency (high frequency) to the total application time), the stress value of the silicon oxide film 210 is decreased. On the other hand, by reducing the ratio of the time for applying AC power at the first frequency (low frequency) to the total application time (increasing the ratio of the time for applying AC power at the second frequency (high frequency) to the total application time), the stress value of the silicon oxide film 210 is increased.

[0042] Here, when the stress value of the silicon oxide film 210 is a tensile stress which is a stress in the direction that the film contracts, the sign of the value is positive (+), and the value increases as the degree of tension increases. On the other hand, when the stress value of the silicon oxide film 210 is a compressive stress which is a stress in the direction that the film expands, the sign of the value is negative (-), and the value decreases as the degree of compression increases.

[0043] Furthermore, in the silicon oxide film forming method of the present embodiment, among the step of applying AC power at the first frequency (low frequency) and the step of applying AC power at the second frequency (high frequency), the step of applying AC power at the first frequency (low frequency) is performed first, and thereafter, the step of applying AC power at the first frequency (low frequency) and the step of applying AC power at the second frequency (high frequency) are performed by alternately switching therebetween.

[0044] Furthermore, in the silicon oxide film forming method of the present embodiment, in the step of introducing a processing gas from the gas introduction unit 35, tetraethoxysilane (TEOS) gas is introduced.

[0045] In this embodiment, as shown in Figure 2, the silicon oxide film formation method involves, in step S1, introducing a processing gas for forming a silicon oxide film 210 into a processing chamber 10 that has been heated by heaters 61 and 62. In step S2, AC power of a first frequency (low frequency) is applied to the gas introduction section 35 for a predetermined time. As a result, a first layer 211 (Figure 3) is laminated onto the substrate 200.

[0046] In step S3, AC power of a second frequency (high frequency) is applied to the gas introduction section 35 for a second predetermined time. As a result, the second layer 212 (Figure 3) is laminated onto the substrate 200. Also, between steps S2 and S3, the AC power applied to the gas introduction section 35 is switched from a first frequency (low frequency) to a second frequency (high frequency). The first predetermined time for which AC power of the first frequency (low frequency) is applied and the second predetermined time for which AC power of the second frequency (high frequency) is applied are set based on the target stress value of the silicon oxide film 210 that is formed.

[0047] In step S4, it is determined whether the application of AC power at the first frequency (low frequency) and the application of AC power at the second frequency (high frequency) have been switched the set number of times. If the set number of switches has been made, the process returns to step S5. If the set number of switches has not been reached, the process returns to step S2. In this case, the AC power applied to the gas introduction section 35 is switched from the second frequency (high frequency) to the first frequency (low frequency). The process from steps S2 to S4 is then repeated until the set number of switches is reached.

[0048] As shown in Figure 3, the silicon oxide film 210 formed by the silicon oxide film formation method of this embodiment comprises a first layer 211 formed by applying AC power of a first frequency (low frequency) and a second layer 212 formed by applying AC power of a second frequency (high frequency). Multiple layers of the first layer 211 and the second layer 212 are stacked alternately. Furthermore, in this embodiment, the change in film stress of the silicon oxide film 210 is 20 MPa or less after 1 day and 4 days have elapsed since the formation of the silicon oxide film 210.

[0049] In other words, in this embodiment, the silicon oxide film 210 comprises a first layer 211 having compressive stress and a second layer 212 having tensile stress. Furthermore, multiple layers of the first layer 211 and the second layer 212 are stacked alternately. When multiple layers of the first layer 211 and the second layer 212 are stacked, the film has a tensile stress of +100 MPa or more, and the change in film stress is 20 MPa or less after 1 day and 4 days have elapsed since formation.

[0050] (Examples) Next, examples of the present invention will be described with reference to Figures 4 to 15.

[0051] In the embodiment, a silicon oxide film 210 was formed on a substrate 200 using a substrate processing apparatus 100 according to the embodiment. In the embodiment, results were obtained regarding the change in the stress value of the formed silicon oxide film over time. In the embodiment, results were also obtained regarding the etching rate of the formed silicon oxide film. The environment in which the stress value of the formed silicon oxide film was measured and the environment in which the substrate was left to measure the change over time was an atmospheric environment at room temperature (23±2°C) and humidity of 30% to 60%. The environment in which the etching rate was measured was also at room temperature (23±2°C).

[0052] The change in stress value of the silicon oxide film over time was obtained by measuring the stress value immediately after deposition (within 10 minutes after deposition) and the stress value after a predetermined time had elapsed since deposition. The stress value of the silicon oxide film was calculated based on the amount of warpage of the substrate 200 on which the silicon oxide film was formed. A thin-film stress measuring device (Toho Technology Co., Ltd., model "FLX-2320-S") was used to measure the stress value of the silicon oxide film.

[0053] The etching rate of the silicon oxide film was calculated by treating the formed silicon oxide film with a chemical solution (9:1 HF (hydrogen fluoride)) and measuring the amount etched per unit time (film thickness). Furthermore, since the etching rate of the silicon oxide film depends on the treatment time and the concentration of the chemical solution, it was calculated as a ratio to the etching rate of the thermal oxide film (TOX) treated simultaneously. That is, the etching rate was obtained as a ratio by dividing the measured etching rate of the silicon oxide film by the etching rate of the thermal oxide film (TOX). In other words, a ratio of 1 means that the etching rate of the silicon oxide film is equal to that of the thermal oxide film (TOX). A spectroscopic ellipsometer thin film material evaluation system (Sentech, model "SENresearch 4.0") was used to measure the film thickness of the silicon oxide film for calculating the etching rate.

[0054] In the embodiments shown in Figures 4 and 5, a silicon oxide film was formed on the substrate 200 by repeatedly switching the AC power applied to the upper gas introduction section 35 between a first frequency (low frequency) and a second frequency (high frequency). Furthermore, a silicon oxide film was formed on the substrate 200 by varying the application time of the AC power at the first frequency (low frequency) and the application time of the AC power at the second frequency (high frequency). In the embodiments shown in Figures 4 and 5, the lower electrode (stage 21) was grounded. The horizontal axis in the graphs of Figures 4 and 5 represents the ratio (%) of the application time of AC power at the second frequency (high frequency) to the total application time (sum of the application time of AC power at the first frequency (low frequency) and the application time of AC power at the second frequency (high frequency)).

[0055] Furthermore, in the embodiments shown in Figures 4 and 5, oxygen (O ２ A gas was supplied at a flow rate of 750 sccm, tetraethoxysilane (TEOS) gas at a flow rate of 15 sccm, and helium gas at a flow rate of 1000 sccm. In addition, AC power at a first frequency (low frequency) was applied at a frequency of 380 kHz and a power of 200 W, and AC power at a second frequency (high frequency) was applied at a frequency of 13.56 MHz and a power of 25 W.

[0056] In the embodiment, as shown in Figure 4, it was found that the stress value of the formed silicon oxide film can be easily adjusted (controlled) by changing the ratio of the application time of AC power at a first frequency (low frequency) to the application time of AC power at a second frequency (high frequency). Furthermore, in the embodiment, it was found that by changing the ratio of the application time of AC power at a first frequency (low frequency) to the application time of AC power at a second frequency (high frequency), it is possible to adjust the film stress to a tensile stress such that the stress value of the silicon oxide film is positive (+), and also to adjust the film stress to a compressive stress such that the stress value of the silicon oxide film is negative (-).

[0057] Furthermore, as shown in Figure 4, in the embodiment, it was found that the stress value of the silicon oxide film remained virtually unchanged after 1 day and 4 days compared to immediately after deposition (within 10 minutes after deposition). In other words, it was found that by alternately switching between the process of applying AC power of a first frequency (low frequency) and the process of applying AC power of a second frequency (high frequency), a silicon oxide film with suppressed changes in stress value over time can be obtained without forming a modified layer. Specifically, when the ratio (%) of the application time of AC power of the second frequency (high frequency) to the total application time was between approximately 10% and approximately 95%, the change in film stress (decrease) of the silicon oxide film after 1 day was less than 10 MPa. Furthermore, when the ratio (%) of the application time of the second frequency (high frequency) AC power to the total application time was between approximately 10% and approximately 95%, the change in film stress (decrease) of the silicon oxide film after 4 days was less than 17 MPa (i.e., 20 MPa or less). In addition, in this embodiment, by setting the first frequency (low frequency) AC power to 200 W, the stress value of the silicon oxide film of the first layer 211 (immediately after film formation) is a compressive stress of -150 MPa or less. This also makes it possible to reduce the change in film stress (decrease) of the silicon oxide film.

[0058] Furthermore, as shown in Figure 5 of the embodiment, it was found that the etching rate of the formed silicon oxide film can be easily adjusted (controlled) by changing the ratio of the application time of AC power at the first frequency (low frequency) to the application time of AC power at the second frequency (high frequency). In other words, it was found that the etching rate increases as the proportion of the application time of AC power at the second frequency (high frequency) increases. In addition, as shown in Figures 4 and 5, the silicon oxide film according to the embodiment shows a change (change over time) of 20 MPa or less after 4 days, and there is a correlation that the etching rate increases as the film stress increases. In particular, as shown in Figures 4 and 5, the silicon oxide film according to the embodiment shows a change (change over time) of 20 MPa or less after 4 days even when the film stress has a tensile stress of +100 MPa or more.

[0059] (Comparative Example 1) In Comparative Example 1 shown in Figures 6 and 7, a silicon oxide film was formed on the substrate 200 by applying only the second frequency (high frequency) AC power to the upper gas inlet 35. In addition, a silicon oxide film was formed on the substrate 200 by varying the power of the second frequency (high frequency) AC power applied to the upper gas inlet 35. The horizontal axis in the graphs of Figures 6 and 7 represents the power of the second frequency (high frequency) AC power applied to the upper gas inlet 35.

[0060] Furthermore, in Comparative Example 1 shown in Figures 6 and 7, oxygen (O ２ A gas was supplied at a flow rate of 750 sccm, tetraethoxysilane (TEOS) gas at a flow rate of 15 sccm, and helium gas at a flow rate of 1000 sccm. In addition, AC power at a second frequency (high frequency) was applied at a frequency of 13.56 MHz.

[0061] In Comparative Example 1, as shown in Figure 6, even when the power of the second frequency (high frequency) AC power applied to the upper gas introduction section 35 is changed, no correlation can be found in the stress values ​​of the formed silicon oxide film. Therefore, it is difficult to adjust the stress values ​​of the formed silicon oxide film.

[0062] Furthermore, in Comparative Example 1, as shown in Figure 6, it can be seen that the stress value of the silicon oxide film changed significantly after 3 days (after time had passed) compared to immediately after deposition (within 10 minutes after deposition). Specifically, when only the second frequency (high frequency) AC power was applied to the upper gas inlet 35, the change (decrease) in the film stress of the silicon oxide film after 3 days was a maximum of approximately 190 MPa. In addition, it can be seen that, regardless of the power of the second frequency (high frequency) AC power applied to the upper gas inlet 35, the stress value of the silicon oxide film immediately after deposition was always tensile stress (stress value was positive (+)), and that the change in the stress value of the silicon oxide film over time was large (it changed easily over time).

[0063] Furthermore, in Comparative Example 1, as shown in Figure 7, even when the power of the second frequency (high frequency) AC power applied to the upper gas introduction section 35 is changed, no correlation can be found in the etching rate of the formed silicon oxide film. Therefore, it is difficult to adjust the etching rate of the formed silicon oxide film.

[0064] (Comparative Example 2) In Comparative Example 2, shown in Figures 8 and 9, a silicon oxide film was formed on the substrate 200 by applying only a first frequency (low frequency) AC power to the upper gas inlet 35. In addition, a silicon oxide film was formed on the substrate 200 by varying the power of the first frequency (low frequency) AC power applied to the upper gas inlet 35. The horizontal axis in the graphs of Figures 8 and 9 represents the power of the first frequency (low frequency) AC power applied to the upper gas inlet 35.

[0065] Furthermore, in Comparative Example 2 shown in Figures 8 and 9, oxygen (O ２ A gas was supplied at a flow rate of 750 sccm, tetraethoxysilane (TEOS) gas at a flow rate of 15 sccm, and helium gas at a flow rate of 1000 sccm. In addition, AC power at a first frequency (low frequency) was applied at a frequency of 380 kHz.

[0066] In Comparative Example 2, as shown in Figure 8, even when the power of the first frequency (low frequency) AC power applied to the upper gas introduction section 35 is changed, no correlation can be found in the stress values ​​of the formed silicon oxide film. Therefore, it is difficult to adjust the stress values ​​of the formed silicon oxide film.

[0067] Furthermore, in Comparative Example 2, as shown in Figure 8, it can be seen that the stress value of the silicon oxide film changed significantly after 3 days (after time had passed) compared to immediately after deposition (within 10 minutes after deposition). Specifically, when the AC power applied to the upper gas introduction section 35 was only at the first frequency (low frequency), the change (decrease) in the film stress of the silicon oxide film after 3 days was a maximum of approximately 290 MPa. In addition, it can be seen that when the stress value of the silicon oxide film immediately after deposition is at least approximately -100 MPa or higher (larger on the tensile side than approximately -100 MPa), the change in the stress value of the silicon oxide film over time is large (it is prone to change over time).

[0068] Furthermore, in Comparative Example 2, as shown in Figure 9, it was found that the etching rate of the formed silicon oxide film could be adjusted by changing the power of the first frequency (low frequency) AC power applied to the upper gas introduction section 35. In other words, it was found that the etching rate decreased as the power of the first frequency (low frequency) AC power applied to the upper gas introduction section 35 increased. In Comparative Example 2, when the first frequency (low frequency) AC power was set to 200W, the stress value of the silicon oxide film (immediately after film formation) was -150 MPa or less in the compressive direction. This condition is the same as the condition for stacking the first layer 211 in the embodiment shown in Figures 4 and 5.

[0069] (Comparative Example 3) In Comparative Example 3 shown in Figures 10 and 11, the AC power applied to the upper gas introduction section 35 was set to the second frequency (high frequency), and the AC power applied to the lower stage 21 was set to a low frequency to form a silicon oxide film on the substrate 200. In addition, the power of the low frequency AC power applied to the lower stage 21 was varied to form a silicon oxide film on the substrate 200 in each case. The horizontal axis in the graphs in Figures 10 and 11 represents the power of the low frequency AC power applied to the lower stage 21.

[0070] Furthermore, in Comparative Example 3 shown in Figures 10 and 11, oxygen (O ２ A gas was supplied at a flow rate of 750 sccm, tetraethoxysilane (TEOS) gas at a flow rate of 15 sccm, and helium gas at a flow rate of 1000 sccm. In addition, a second frequency (high frequency) AC power was applied to the upper gas inlet 35 at a frequency of 13.56 MHz and a power of 25 W. In addition, a low frequency AC power was applied to the lower stage 21 at a frequency of 380 kHz.

[0071] In Comparative Example 3, as shown in Figure 10, no correlation was found in the stress values ​​of the formed silicon oxide film even when the power of the low-frequency AC power applied to the lower stage 21 was changed, making it difficult to adjust the stress values ​​of the formed silicon oxide film. However, focusing only on the stress values ​​of the silicon oxide film immediately after deposition, it was found that the stress values ​​of the silicon oxide film decreased (shifted towards compressive stress) as the power of the low-frequency AC power applied to the lower stage 21 increased.

[0072] Furthermore, in Comparative Example 3, as shown in Figure 10, it can be seen that the stress value of the silicon oxide film changed significantly after 3 days (after time had passed) compared to immediately after film formation (within 10 minutes after film formation). Specifically, when the AC power applied to the upper gas introduction section 35 was set to the second frequency (high frequency) and the AC power applied to the lower stage 21 was set to a low frequency, the change in film stress (decrease) of the silicon oxide film after 3 days was a maximum of approximately 260 MPa. In addition, it can be seen that when the stress value of the silicon oxide film immediately after film formation is at least approximately -100 MPa or higher (larger on the tensile side than approximately -100 MPa), the change in the stress value of the silicon oxide film over time is large (it is prone to change over time).

[0073] Furthermore, in Comparative Example 3, as shown in Figure 11, it was found that the etching rate of the silicon oxide film formed could be adjusted by changing the power of the low-frequency AC power applied to the lower stage 21. In other words, it was found that the etching rate decreased as the power of the low-frequency AC power applied to the lower stage 21 increased.

[0074] (Comparative Example 4) In Comparative Example 4 shown in Figures 12 and 13, the AC power applied to the upper gas inlet 35 was set to a second frequency (high frequency), and the AC power applied to the lower stage 21 was set to a low frequency to form a silicon oxide film on the substrate 200. In addition, the power of the second frequency (high frequency) AC power applied to the upper gas inlet 35 was varied to form a silicon oxide film on the substrate 200 in each case. The horizontal axis in the graphs in Figures 12 and 13 represents the power of the second frequency (high frequency) AC power applied to the upper gas inlet 35.

[0075] Furthermore, in Comparative Example 4 shown in Figures 12 and 13, oxygen (O ２A gas was supplied at a flow rate of 750 sccm, tetraethoxysilane (TEOS) gas at a flow rate of 15 sccm, and helium gas at a flow rate of 1000 sccm. In addition, a second frequency (high frequency) AC power was applied to the upper gas inlet 35 at a frequency of 13.56 MHz. In addition, a low frequency AC power was applied to the lower stage 21 at a frequency of 380 kHz and a power of 50 W.

[0076] In Comparative Example 4, as shown in Figure 12, no correlation was found in the stress values ​​of the formed silicon oxide film even when the power of the second frequency (high frequency) AC power applied to the upper gas introduction section 35 was changed, making it difficult to adjust the stress values ​​of the formed silicon oxide film. However, focusing only on the stress values ​​of the silicon oxide film immediately after deposition, it was found that in an environment where low frequency AC power was applied to the lower stage 21, the stress values ​​of the silicon oxide film decreased (shifted towards compressive stress) as the power of the AC power applied to the upper gas introduction section 35 increased.

[0077] Furthermore, in Comparative Example 4, as shown in Figure 12, it can be seen that the stress value of the silicon oxide film changed significantly after 3 days (after time had passed) compared to immediately after deposition (within 10 minutes after deposition). Specifically, when the AC power applied to the upper gas introduction section 35 was set to the second frequency (high frequency) and the AC power applied to the lower stage 21 was set to a low frequency, the change in film stress (decrease) of the silicon oxide film after 3 days was a maximum of approximately 240 MPa. In addition, it can be seen that when the stress value of the silicon oxide film immediately after deposition is at least approximately -50 MPa or higher (larger on the tensile side than approximately -50 Pa), the change in the stress value of the silicon oxide film over time is large (it is prone to change over time).

[0078] Furthermore, in Comparative Example 4, as shown in Figure 13, it was found that the etching rate of the formed silicon oxide film could be adjusted by changing the power of the second frequency (high frequency) AC power applied to the upper gas introduction section 35. In other words, it was found that the etching rate decreased as the power of the second frequency (high frequency) AC power applied to the upper gas introduction section 35 increased.

[0079] (Relationship between etching rate and film stress) As shown in Figure 14, in the relationship between etching rate and film stress, immediately after film formation, a correlation can be found in Example, Comparative Example 2, Comparative Example 3, and Comparative Example 4, where the etching rate increases as the film stress increases. As shown in Figure 15, in the relationship between etching rate and film stress, after time has passed, a correlation can be found in Example, where the etching rate increases as the film stress increases. Furthermore, comparing Figures 14 and 15, it can be seen that in Comparative Examples 1 to 4, the change in the stress value of the silicon oxide film over time is large when the stress value of the silicon oxide film immediately after film formation is above a certain level (for example, a stress greater on the tensile side than approximately -100 MPa to -50 MPa (low stress region)) or when the etching rate is above a certain level. In other words, under the processing conditions shown in Comparative Examples 1 to 4 (upper high-frequency application, upper low-frequency application, upper high-frequency and lower low-frequency application), it was found that silicon oxide films with low stress values ​​(generally -100 MPa to +100 MPa) have difficulty suppressing the change in stress value over time. Furthermore, as shown in Figures 14 and 15, the silicon oxide films according to the examples show a change (change over time) of 20 MPa or less after 4 days, and there is a correlation that the etching rate increases as the film stress increases.

[0080] (Effects of this embodiment) In this embodiment, the following effects can be obtained.

[0081] In the silicon oxide film formation method of this embodiment, as described above, the process of applying AC power of a first frequency to the gas introduction section 35 and the process of applying AC power of a second frequency, which has a higher frequency than the first frequency, to the gas introduction section 35 are alternately switched between. This makes it possible to form a silicon oxide film in which the change in stress value over time is suppressed. As a result, since there is no need to provide a step for forming a modified layer, the production efficiency (throughput) of the silicon oxide film in which the change in stress value over time is suppressed can be improved. In addition, since AC power of a relatively low frequency is not applied to the stage 21 on which the substrate 200 is placed, it is possible to suppress the high-energy collision of the plasma-generated processing gas with the substrate 200. As a result, it is possible to suppress defects in the substrate 200 caused by plasma collisions.

[0082] Furthermore, in this embodiment, as described above, the process of applying AC power of the first frequency and the process of applying AC power of the second frequency are alternately switched to be performed multiple times each. This makes it possible to form a total of four or more layers of silicon oxide film by applying AC power of the first frequency and AC power of the second frequency, thereby stabilizing the film quality of the silicon oxide film.

[0083] Furthermore, in this embodiment, as described above, the process involves applying AC power of a first frequency and applying AC power of a second frequency. First, the process of applying AC power of a first frequency is performed, and then the process of applying AC power of a first frequency and the process of applying AC power of a second frequency are alternately performed. As a result, a silicon oxide film layer is formed by first applying AC power of a relatively low frequency, the first frequency, so that a layer with compressive stress can be formed on the substrate 200 first. This makes it easier for the silicon oxide film to adhere to the substrate 200.

[0084] Furthermore, in this embodiment, as described above, tetraethoxysilane (TEOS) gas is introduced in the step of introducing the processing gas from the gas introduction section 35. This allows the tetraethoxysilane (TEOS) gas to be plasma-generated, making it possible to easily form a silicon oxide film on the substrate 200 with suppressed changes in stress values ​​over time.

[0085] Furthermore, in this embodiment, as described above, the stress value of the formed silicon oxide film is adjusted by adjusting the ratio of the application time between the step of applying AC power of the first frequency and the step of applying AC power of the second frequency. As a result, a silicon oxide film having a desired stress value and in which the change in stress value over time is suppressed can be formed on the substrate 200.

[0086] (Modifications) It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than the description of the embodiments above, and further includes all modifications (modifications) within the meaning and scope equivalent to the claims.

[0087] For example, in the above embodiment, an example was shown in which the silicon oxide film formation method is carried out using the substrate processing apparatus 100 shown in Figure 1 as the silicon oxide film formation apparatus, but the present invention is not limited thereto. The apparatus configuration of the substrate processing apparatus (silicon oxide film formation apparatus) for carrying out the silicon oxide film formation method of the present invention is not particularly limited and may differ from the apparatus configuration shown in Figure 1.

[0088] Furthermore, although the above embodiment shows an example of a configuration in which the gas introduction unit for introducing the processing gas is placed above the substrate and the substrate is placed below it, the present invention is not limited to this. In the present invention, the gas introduction unit for introducing the processing gas may be placed below the substrate and the substrate may be placed above it. In other words, the gas introduction unit to which AC power of a first frequency (low frequency) and AC power of a second frequency (high frequency) are alternately applied may be placed below the substrate.

[0089] Furthermore, while the above embodiment shows an example of a configuration in which the first step of applying AC power at a first frequency (low frequency) and the second step of applying AC power at a second frequency (high frequency) are performed first, the present invention is not limited to this. In the present invention, the second step of applying AC power at a second frequency (high frequency) may be performed first, among the steps of applying AC power at a first frequency (low frequency) and the second step of applying AC power at a second frequency (high frequency). In particular, if there is concern about plasma damage due to the substrate surface being directly exposed to the plasma, it is preferable to apply AC power at a second frequency (high frequency) first. When the frequency of the AC power applied to the gas introduction section is high frequency, the potential switching at the gas introduction section is faster than at low frequency, and although electrons move toward the substrate, ions have a much larger mass than electrons, so ions in the plasma cannot keep up with the potential switching at the gas introduction section and are less likely to move toward the substrate. Therefore, even if the substrate surface is directly exposed to the plasma, high frequency results in less plasma damage than low frequency.

[0090] Furthermore, while the above embodiment shows an example configuration in which the steps of applying AC power of a first frequency (low frequency) and applying AC power of a second frequency (high frequency) are performed an equal number of times, the present invention is not limited to this. In the present invention, one of the steps of applying AC power of a first frequency (low frequency) and applying AC power of a second frequency (high frequency) may be performed a greater number of times than the other (for example, 1). In other words, AC power of a first frequency (low frequency) may be applied first, then the steps of applying AC power of a first frequency (low frequency) and applying AC power of a second frequency (high frequency) may be alternately switched, and finally, AC power of a first frequency (low frequency) may be applied to end the process. Alternatively, the process may be completed by first applying AC power of a second frequency (high frequency), then alternately switching between applying AC power of a first frequency (low frequency) and AC power of a second frequency (high frequency), and finally applying AC power of a second frequency (high frequency) to finish the process.

[0091] Furthermore, in the above embodiment, an example of a configuration in which a silicon oxide film is formed using tetraethoxysilane (TEOS) gas has been shown, but the present invention is not limited thereto. In the present invention, silane (SiH ４ ) gas and dinitrogen monoxide (N ２ O) gas may be used to form a silicon oxide film by alternately switching between a step of applying AC power of a first frequency (lower frequency) to a gas introduction unit and a step of applying AC power of a second frequency (higher frequency) to the gas introduction unit.

[0092] [Aspect] It will be understood by those skilled in the art that the above exemplary embodiments are specific examples of the following aspects.

[0093] (Item 1) A method for forming a silicon oxide film, comprising: a step of introducing a processing gas for forming a silicon oxide film onto a substrate to be processed in a processing chamber from a gas introduction unit; a step of applying AC power of a first frequency to the gas introduction unit; and a step of applying AC power of a second frequency, which has a higher frequency than the first frequency, to the gas introduction unit, wherein the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately switched and performed.

[0094] (Item 2) The method for forming a silicon oxide film according to Item 1, wherein the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately switched so as to be each performed a plurality of times.

[0095] (Item 3) The method for forming a silicon oxide film according to Item 1 or 2, wherein among the step of applying AC power of the first frequency and the step of applying AC power of the second frequency, the step of applying AC power of the first frequency is performed first, and thereafter the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately switched and performed.

[0096] (Item 4) The method for forming a silicon oxide film according to any one of Items 1 to 3, wherein in the step of introducing the processing gas from the gas introduction unit, tetraethoxysilane (TEOS) gas is introduced.

[0097] (Item 5) A method for forming a silicon oxide film according to any one of Items 1 to 4, wherein the stress value of the formed silicon oxide film is adjusted by adjusting the ratio of the application time between the step of applying AC power of the first frequency and the step of applying AC power of the second frequency.

[0098] (Item 6) A silicon oxide film forming apparatus comprising: a processing chamber in which a substrate to be processed is placed; a gas introduction unit for introducing a processing gas for forming a silicon oxide film on the substrate in the processing chamber; an AC power application unit for applying AC power to the gas introduction unit; and a control unit, wherein the control unit controls the introduction of the processing gas from the gas introduction unit and controls the alternating switching of the AC power applied from the AC power application unit between AC power of a first frequency and AC power of a second frequency having a higher frequency than the first frequency.

[0099] (Item 7) A silicon oxide film comprising a first layer having compressive stress and a second layer having tensile stress, wherein the first layer and the second layer are stacked alternately in multiple layers, and in the state in which the first layer and the second layer are stacked, the film has a tensile stress of +100 MPa or more, and the amount of change in film stress after 1 day has elapsed since formation is 20 MPa or less.

[0100] (Item 8) A silicon oxide film comprising a first layer having compressive stress and a second layer having tensile stress, wherein the first layer and the second layer are stacked alternately in multiple layers, and the first layer has a film stress in the compressive direction of -150 MPa or less.

[0101] 10: Processing chamber, 35: Gas introduction unit, 41: Low-frequency power application unit (AC power application unit), 42: High-frequency power application unit (AC power application unit), 70: Control unit, 100: Substrate processing apparatus (silicon oxide film forming apparatus), 200: Substrate, 210: Silicon oxide film, 211: First layer, 212: Second layer

Claims

1. A silicon oxide film formation method comprising: a step of introducing a processing gas for forming a silicon oxide film on a substrate to be processed in a processing chamber from a gas inlet; a step of applying AC power of a first frequency to the gas inlet; and a step of applying AC power of a second frequency having a higher frequency than the first frequency to the gas inlet, wherein the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately switched.

2. The silicon oxide film forming method according to claim 1, wherein the step of applying AC power of the first frequency and the step of applying AC power of the second frequency are alternately switched to be performed multiple times each.

3. The silicon oxide film forming method according to claim 1 or 2, wherein, of the steps of applying AC power of a first frequency and applying AC power of a second frequency, the step of applying AC power of a first frequency is performed first, and then the steps of applying AC power of a first frequency and applying AC power of a second frequency are alternately switched.

4. The silicon oxide film formation method according to any one of claims 1 to 3, wherein in the step of introducing the processing gas from the gas introduction section, tetraethoxysilane (TEOS) gas is introduced.

5. A method for forming a silicon oxide film according to any one of claims 1 to 4, wherein the stress value of the formed silicon oxide film is adjusted by adjusting the ratio of the application time between the step of applying AC power of the first frequency and the step of applying AC power of the second frequency.

6. A silicon oxide film forming apparatus comprising: a processing chamber in which a substrate to be processed is placed; a gas introduction unit for introducing a processing gas for forming a silicon oxide film on the substrate in the processing chamber; an AC power application unit for applying AC power to the gas introduction unit; and a control unit, wherein the control unit controls the introduction of the processing gas from the gas introduction unit and controls the alternating switching of the AC power applied from the AC power application unit between AC power of a first frequency and AC power of a second frequency having a higher frequency than the first frequency.

7. A silicon oxide film comprising a first layer having compressive stress and a second layer having tensile stress, wherein the first and second layers are stacked alternately in multiple layers, and in the state where the first and second layers are stacked in multiple layers, the film has a tensile film stress of +100 MPa or more, and the amount of change in film stress after 1 day has elapsed since formation is 20 MPa or less.

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